Abstract:

ased on the temperature and measured meteorological data during the frost-free period at the 9 meteorological stations in southwestern Shandong from 1961 to 2015, the spatio-temporal change characteristics of heat resources during the period Ι (1961-1990）and the period Π（1991-2015）were analyzed using a linear regression method, Mann-Kendall break detector and independent research drawing software (Eqlds 2015). The results show that the active accumulated temperature ≥0 ℃,≥5 ℃ and ≥10 ℃ all show significant increasing trend（p<0.01）with the climate tendency rate of 66.4 ℃•d /10 a, 54.3 ℃•d /10 a and 88.6 ℃•d /10 a from 1961 to 2015, respectively. The duration of the frost-free period is between 286 d and 304 d and shows an increasing trend with a rate of 1.0 d /10 a. The annual average temperature and accumulated temperature all decrease with increase of latitude  and are higher in southeastern counties such as Caoxian, Chengwu and Shanxian county and are lower in northern counties like Juancheng and Yuncheng county. The frost-free period has no significant linear relationship with altitude and its change shows a certain regional characteristic. The heat resources occur abrupt climatic change in the 1990s and then significantly increase. In addition, the active accumulated temperature and the frost-free period during the period Π are 169.4-301.2 ℃•d higher and 3 d longer than those during the period Ι, respectively. As a result, the heat resources of period Π are higher than those of period Ι.

Key words: Heat resources, Linear regression method, Frost-free period, Southwestern Shandong province